Siemens siprotec 7SA522, User Manual

Page: 236 / 628

Functions
6-88
7SA522 Manual
C53000-G1176-C119-2
attenuation of the transmitted signal could be so severe at the fault location, that re-
ception at the other line end cannot necessarily be guaranteed.
Figure 6-52 shows the operation scheme.
Faults inside the overreaching zone Z1B, which is set to approximately 120% of the
line length, will initiate tripping if a blocking signal is not received from the other line
end. On three terminal lines, Z1B must be set to reliably reach beyond the longer line
section, even if there is an additional infeed via the tee point. Due to possible differ-
ences in the pick-up times of the devices at the two line ends, and because of the sig-
nal transmission time, the tripping must in this case be somewhat delayed by means
of T
V
(address ,
5HOHDVH'HOD\
).
Similarly, to avoid race conditions of the signals, a transmit signal can be prolonged
by the settable time T
S
once it has been initiated.
Figure 6-52 Operation scheme of the blocking method
Sequence Figure 6-53 shows the logic diagram of the blocking scheme for one line end.
The relevant distance zone for this scheme is the overreach zone Z1B. Its reach di-
rection must therefore be set to
)RUZDUG
: In the case of distance protection with po-
lygonal characteristic, in address
2SPRGH=%
, refer also to Sub-section
6.2.3.2 under margin heading “Controlled Zone Z1B”; in the case of distance protec-
tion with MHO characteristic, in address
2SPRGH=%
, refer also to Sub-sec-
tion 6.2.4.2 under margin heading “Controlled Zone Z1B”.
On two terminal lines, the signal transmission may be phase segregated. Send and
receive circuits in this case are built up for each phase. On three terminal lines the
send signal is transmitted to both opposite ends. The receive signal are then com-
bined with the logical
OR
function, as in the case of an internal fault, no blocking signal
must be received from any line end. Via the setting
/LQH&RQILJ
(address )
the device is informed as to whether it has one or two opposite line ends.
A B
Z1(A)
Z1(B)
Z1B(A)
Z1B(B)
Z1B
T1B
≥
1
trip
rec.
further
zones
&
Z1 or
d
dt
40 ms
Forw.
(A)
T
S &
≥
1 transm.
(u,i)
FD
(A)
(A)
T
V
≥
1
trip
rec.
further
zones
&
Z1 or
d
dt
40 ms
Forw.
(B)
T
S &
≥
1
transm.
(u,i)
FD
(B)
(B)
T
V
FD (A)
FD (B)
FD (A)
FD (B)
(A)
Z1B
T1B
(B)
FD = Pickup of any set distance zone (Z1 to Z5)